```Python hl_lines="3"
{!../../docs_src/app_testing/test_main.py!}
```

...and have the code for the tests just like before.

## Testing: extended example

Now let's extend this example and add more details to see how to test different parts.

### Extended **FastAPI** app file

Let's continue with the same file structure as before:

```
.
├── app
│   ├── __init__.py

  /** @since 11.0 */
  @Override
  public void put(K key, V value) {
    throw new UnsupportedOperationException();
  }

  /** @since 12.0 */
  @Override
  public void putAll(Map<? extends K, ? extends V> m) {
    for (Entry<? extends K, ? extends V> entry : m.entrySet()) {
      put(entry.getKey(), entry.getValue());
    }
  }

  @Override
  public void cleanUp() {}

  @Override
  public long size() {

 */
@DoNotMock("Use the methods in Futures (like immediateFuture) or SettableFuture")
@ElementTypesAreNonnullByDefault
public interface ListenableFuture<V extends @Nullable Object> extends Future<V> {
  /**
   * Registers a listener to be {@linkplain Executor#execute(Runnable) run} on the given executor.
   * The listener will run when the {@code Future}'s computation is {@linkplain Future#isDone()

 */
@DoNotMock("Use the methods in Futures (like immediateFuture) or SettableFuture")
@ElementTypesAreNonnullByDefault
public interface ListenableFuture<V extends @Nullable Object> extends Future<V> {
  /**
   * Registers a listener to be {@linkplain Executor#execute(Runnable) run} on the given executor.
   * The listener will run when the {@code Future}'s computation is {@linkplain Future#isDone()

  private final StatsAccumulator yStats = new StatsAccumulator();
  private double sumOfProductsOfDeltas = 0.0;

  /** Adds the given pair of values to the dataset. */
  public void add(double x, double y) {
    // We extend the recursive expression for the one-variable case at Art of Computer Programming
    // vol. 2, Knuth, 4.2.2, (16) to the two-variable case. We have two value series x_i and y_i.

      }
      session->graph->mu.unlock();
      status->status = session->session->Extend(std::move(graph_def));
      if (!status->status.ok()) {
        // Contract is we always delete input_values[i].
        return false;
      }
      // Note: session->session is not modified if Extend() fails, so
      // we only set last_num_graph_nodes if it succeeds.
      session->last_num_graph_nodes = num_nodes;

  integrity sha512-mQw+2fkQbALzQ7V0MY0IqdnXNOeTtP4r0lN9z7AAawCXgqea7bDii20AYrIBrFd/Hx0M2Ocz6S111CaFkUcb0Q==

extend@^3.0.0:
  version "3.0.2"
  resolved "https://registry.yarnpkg.com/extend/-/extend-3.0.2.tgz#f8b1136b4071fbd8eb140aff858b1019ec2915fa"
  integrity sha512-fjquC59cD7CyW6urNXK0FBufkZcoiGG80wTuPujX590cB5Ttln20E2UB4S/WARVqhXffZl2LNgS+gQdPIIim/g==

fast-deep-equal@^3.1.1:

                    errors=[error], model=RequestErrorModel
                ).errors()
                use_errors.extend(new_errors)
            elif isinstance(error, list):
                use_errors.extend(_normalize_errors(error))
            else:
                use_errors.append(error)
        return use_errors

    def _model_rebuild(model: Type[BaseModel]) -> None:

 * and {@link State#TERMINATED} states are terminal states, once a service enters either of these
 * states it cannot ever leave them.
 *
 * <p>Implementors of this interface are strongly encouraged to extend one of the abstract classes
 * in this package which implement this interface and make the threading and state management
 * easier.
 *
 * @author Jesse Wilson
 * @author Luke Sandberg

    scheme == other.scheme

internal fun EventListener.asFactory() = EventListener.Factory { this }

/**
 * Reads until this is exhausted or the deadline has been reached. This is careful to not extend the
 * deadline if one exists already.
 */
@Throws(IOException::class)
internal fun Source.skipAll(
  duration: Int,
  timeUnit: TimeUnit,
): Boolean {
  val nowNs = System.nanoTime()